Method of making a coil form



July 26, 1960 W. F. STAHL METHOD OF MAKING A COIL FORM Filed Aug. 19, 1954 \IPIIQIfil/XIIAIIIylliffffylllllli A TTORNEYS "Initial flanges or solder lug collars. flanges are employed, they serve a number of important terminal flangeslZ and '13. each of the terminal flanges has an offset inwardly ex- Itending shoulder 14 about the central opening 15 there- I through("Fig." 4)- 'whichprovides a perimetric' channel U i ed t e P3 fl jO 7 METHOD OF MAKING A'coIL FORM I William F. Stahl, 423 A bbottsford Road, Kenilworth, Ill.

Filed Aug. 19, 195 Ser. No. 450,931 3 Claims. o]. 18-59) This invention relates to a method of making a coil form, and more particularly a method for providing a.

coil form having terminal flanges anchored thereon.

Coil forms are used today in vast quantities as the support structure upon which electric coils are wound. Substantially all of the forms have an elongated core generally equipped at one or .both ends either with ter- Where terminal functions, such as determining the length of the wire coil, mechanically protecting the coilfrom damage and elec- "trically insulating it.. It is important that the flanges be accurately positioned upon the core and firmly anchored V thereto. 1

' An object ofthis invention is to provide a method of making a coil form in which terminal flanges are firmly and accurately secured upon a core. Another object of ,the invention is in providing a method of making a coil form in which the ends of the core are flared or swaged outwardly and in which ridges are provided adjacent the -.a coil form in which the core is impregnated with a ther- ;mosettingresin that is partially cured prior to the positioning of the terminal flanges upon the core, the resin Zbeing cured substantially to completion thereafter while ,.:the flanges and core are brought into tight frictional .engagement. A furtherobject is in providing a method .of making coil forms or bobbins as described, in which .a core impregnated with a thermosetting resin, and being .equipped with terminal flanges, has the endportions jithereof swaged by heated swaging tools, whereby the ,IfiSiIl, at least in the area adjacent the flanges, is cured i120 completion while the core is forced into tight engage- 1116111. with the flanges. rages will appearas the specification proceeds.

Method and structural embodiments of the invention are illustrated in the accompanying drawing, in which- Figure lis a perspective view of a coil form, Fig. 2. is a longitudinal sectional view of a core; Fig. 3 is a broken longitudinal sectional view showing one step in the method wherein a core is heated; Fig. 4 is a longitudi nal sectional View showing terminal flanges being .positioned upon a core; and Fig. 5 is a longitudinal sectional view showing the 'swaging step in the method.

A typical coil form is illustrated in its entirety in Fig. land comprises a core 11 equipped at its ends with In the illustration given,

16 along the outer surface of the flanges about the opening 15. If desired, the flanges 12 and 13 may be provided with apertures 17 therethrough which may serve to accept cap screws in mounting the coil form on a Additional objects and advan- 2,946,096. Patented July 2 6, 1 960 chassis, etc., and may also serve to accept soldering lugs to which the ends of the coil (not shown), may be secured. i

The'core 11 may have any desired cross-sectional configuration and in the drawing the core is shown asbein'g substantially square. The core, however, may beround,

cedures well known to those skilled in the art and which thenwill not be described in detail. For example, the core 11. may be submerged in aclosed tank containing .the resin in solution andIvacuum and pressure alternately applied to the tank to perrheatethe core with the resin.

The terminal flanges 12 and 13 may also have any desired configuration and thecentral opening 15 therethrough will conform to the cross-sectional shape of the core 11 and will be adapted to snugly receive thecore. The flanges will project laterally from the core, as shown in Fig. l, and will serve to c'onfine,.protect mechanically and insulate electrically a coil wound upon the form. The offset shoulder portions 14 may be formed in-the flanges by simply pressing the shoulders outwardly in suitable dies. I

Referring particularly toFig. 5, it is seen that the flanges 12 and 13 are rigidly anchored upon the core 11 by means of the swaged or outwardly flared end portions 18 and 19 at opposite ends of the core and which extend into the peripheral recess '16 providedby the flanges. Inwardly of the flangeslZ and 13, the core 11' 7 provides a raised or outwardly projecting ridge or rib 20 that substantially abuts the inner surface of each flange.

, The flanges then are locked-'or anchored against axial movement relative to the core 11 by the flared ends 18 and l9 and the ridges orribs 20. It is noted. that the core 11 is provided with a longitudinally extending pas- 45 sage 21. through the center thereof which is useful; in

accepting iron cores for theelectric coil and which is also useful in forming the coil form as will be described hereinafter. H v ln' themethod of formi g the coil form 10 a thermosetting resin impregnated core 11 is first provided,-;as ;jis illustrated in Fig. 2. As: is well known, 'thermosetting.

resins have a curing cycle dependent upon time and temperature. When the core-11 is taken from the impregnating solution,.the resin at that vtimegis not cured and is a liquid that is sticky or tacky when touched. The core- 11 in that condition is subjected to a treatment wherein the thermosetting resin is partially cured, and is preferably cured to the extent that it is no longer tacky or sticky and the core can then be handled with relativeease. j

I prefer to partiallycure the resin'by placingthe impregnated core 11 in an oven, suchas shown in Fig. 3 and which is designated. generally with the numeral 22. Suitable ovens are well known in the art and atypical oven, as shown, may include aplatform or conveyor 23 upon which the core 11 is supported, an enclosure member that will-provide a confined oven space," and I which is not shown,;a source heat suchlas the infra- ;I e ll aadr hap rqfl s nnm mher. adjacent the heat source 24 and which functions to direct the heat rays toward the core 11. The time or tempera- 1 I ture, or both, within the oven 22 may be controlled so] that for the period that each of theimpregnated cores'is f warme within the oven, the impregnating resin will obtain a partially cured or semi-cured condition.

After the resin has been partially cured so that the core .11 can-be handled with relativeease, the terminal flanges 12 and 13 are positioned upon thecore as shown in 'Fig. 4. The flanges are moved to preselected points along the core 11 so that thespacing between the .flanges meets the specifications of the user of the core form. The flanges may be mounted either by machine orby hand.

Afteer the flanges have been positioned at desired points upon the core 11, the core and flanges are forced into a tight frictional engagement and the thermosetting resin, at least in the area of the core adjacent the flanges, is substantially completely cured. The curing may be accomplished by heating the core for a period of time, such that the time and temperature cycle for the particular thermosetting resin employed will be satisfied.

I prefer to cure the resin. and at the same time to lock the flanges upon the core by bringing swaging tools 26 and 27 into engagement with the core 11; the swaging tools are heated by any suitable means, as for example, by equipping each of the swaging tools with resistance elements so that the tools will function in a manner similar to a soldering iron and the tips or noses 28 of the tools will then be heated. If desired, the nose portion of each of the tools may have a central chamber 29 therein communicating with a passage 30 through the shaft 31, which in turn is rigidly secured to the nose. temperature fluid may be passed through the passage 30 and into the chamber 29 to heat the nose portion of the swaging tools. As is well known and as is conventional in the art, the swaging tools are provided with a lip 32 adjacent a channel portion 33 which is adapted to receive therein the ends of the core 11.

In simultaneously locking the flanges 12 and 13 upon the core and curing the thermosetting resin, the swaging tools 26 and 27 are inserted into the central passage 21 through the core 11 to bring the end portions of the core into the channels 33 provided by the swaging tools. Force is applied to the tools to move the same toward the center of the core 11 and this will be effective to cause the ends of the core to flare outwardly and into the channels 16 provided by the flanges. Thus, the outwardly flared ends of the core will effectively prevent the flanges from being moved outwardly and olf of the core 11. In the time necessary to accomplish that result, the heated swaging tools will elevate the temperature of the core 11, at least in the area thereof adjacent the flanges and for a suflicient length of time to substantially cure to completion the thermosetting resin. When the swaging tools are withdrawn from the core it is found that the ends of the core are swaged or flared outwardly and that the resin is cured. s

As part of the swaging and curing operation the ridges or ribs may be formed. Preferably, the ridges are provided by employing swaging tools that are slightly larger than those ordinarily used for swaging cores of the same dimensions. Then when these slightly oversize tools are pressed into the core, they are operative to dis tort the core slightly in the area thereof inwardly of the flanges and push it laterally (the area under the flanges being reinforced and confined thereby). The setting or curing of the thermoplastic results in this distortion or formation of the ridge being permanent and, as shown in Fig. 5, the flanges are locked or anchored between these ridges and the swaged ends of the core. The rib is a slightly raised portion that may have a thickness of .002 inch.

The temperature within the curing oven and the time that a core is maintained within the oven can be varied to suit the curing cycle of theparticular plastic impregnat- Relatively high' ing material being used. That is, the curing cycle of thermosetting plastics varies with the characteristics thereof and it is well known in the art that the time and temperature of the curing cycle may be varied as desired so as to provide a very short cycle or a long one. The same is true of the temperature to which the swaging tools are elevated. I have found it desirable to provide a temperature that results in substantially an instantaneous curing'of the resin upon contact of theswaging tools with the core. However, if longer curing cycles are desired, the temperature of the swaging tools may be lowered. In other words, the temperature of the swaging tools and the period of contact thereof with the core may be varied, if desired, to fit any particular manufacturing procedure or to control two tolerances, etc.

The rib or ridge 20 may also be formed in the core 11 by employing swaging tools which have the customary size for a.given tube size and by pushing them inwardly or toward eachother to a greater extent than is usual and to the point where the ends of the core cannot be further flared outwardly, that is, the flared ends will be confined by .the lips 32 of the swaging tools. At this point, the core 11 will buckle slightly and the core distortion will result in the formation of the ridge 20.

While in the foregoing specification embodiments of the method and structure have been described in considerable detail for purposes of illustration, it will be apparent to those skilled in the art that they may make numerous changes in these details without departing from the spirit and teachings of the invention.

I claim:

1. In a method of making a coil form, the steps of impregnating a core with a thermosetting resin, .partially curing the impregnated core to a manipulatable state characterized by the absence of tackiness and stickiness, mounting a flange upon said core in a predetermined position, and substantially simultaneously locking said flange upon said core by deforming said core while curing substantially to completion the impregnating resin, at least in the area of the core adjacent said flange.

2. The method of claim 1, in which a pair of flanges are mounted on said core in spaced relation to each other and adjacent the ends of said core.

3. In a method of making a coil form, the steps of partially curing the impregnating resin of a fibrous core impregnated with a thermosetting resin to a condition wherein the surface of said impregnated core is characterized by the absence of tackincss and stickiness when manipulated, manipulating said core to mount at least one terminal flange thereon, and simultaneously heating said core in the area of said flange and swaging said core to form a flared end on one side of the flange and a raised rib on the other to anchor the flange on said core.

'References Cited in thefile of this patent UNITED STATES PATENTS 1,370,800 Egerton Mar. 8, 1921 1,528,445 Marshall Mar. 3, 1925 1,589,177 Kendall June 15, 1926 2,228,930 Robinson Ian. 14, 1941 2,266,420 Gardner Dec. 16, 1941 2,343,389 Stahl Mar. 7, 1944 2,375,704 Stahl May 8, 1945 2,431,238 Friedman Nov. 18, 1947 2,546,208 Barton Mar. 27, 1951 2,644,651 Stahl et al. July 7, 1953 2,654,549 Rappleyea Oct. 6, 1953 2,678,471 Barton May 18, 1954 2,689,400 Mirando Sept. 21, 1954 

1. IN A METHOD OF MAKING A COIL FORM, THE STEPS OF IMPREGNATING A CORE WITH A THERMOSETTING RESIN, PARTIALLY CURING THE IMPREGNATED CORE TO A MANIPULATABLE STATE CHARACTERIZED BY THE ABSENCE OF TACKINESS AND STICKINESS, MOUNTING A FLANGE UPON SAID CORE IN A PREDETERMAINED POSITION, AND SUBSTANTIALLY SIMULTANEOUSLY LOCKING SAID FLANGE UPON SAID CORE BY DEFORMING SAID CORE WHILE CURING SUBSTANTIALLY TO COMPLETION THE INPREGNATING RESIN, AT LEAST IN THE AREA OF THE CORE ADJACENT SAID FLANGE. 